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-rw-r--r--lib/VMCore/DominatorInternals.cpp140
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diff --git a/lib/VMCore/DominatorInternals.cpp b/lib/VMCore/DominatorInternals.cpp
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--- a/lib/VMCore/DominatorInternals.cpp
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-//==- DominatorInternals.cpp - Dominator Calculation -------------*- C++ -*-==//
-//
-// The LLVM Compiler Infrastructure
-//
-// This file was developed by Owen Anderson and is distributed under
-// the University of Illinois Open Source License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/Analysis/Dominators.h"
-#include "llvm/ADT/DenseMap.h"
-#include "llvm/ADT/SmallPtrSet.h"
-//===----------------------------------------------------------------------===//
-//
-// DominatorTree construction - This pass constructs immediate dominator
-// information for a flow-graph based on the algorithm described in this
-// document:
-//
-// A Fast Algorithm for Finding Dominators in a Flowgraph
-// T. Lengauer & R. Tarjan, ACM TOPLAS July 1979, pgs 121-141.
-//
-// This implements both the O(n*ack(n)) and the O(n*log(n)) versions of EVAL and
-// LINK, but it turns out that the theoretically slower O(n*log(n))
-// implementation is actually faster than the "efficient" algorithm (even for
-// large CFGs) because the constant overheads are substantially smaller. The
-// lower-complexity version can be enabled with the following #define:
-//
-#define BALANCE_IDOM_TREE 0
-//
-//===----------------------------------------------------------------------===//
-
-namespace llvm {
-
-void Compress(DominatorTreeBase& DT, BasicBlock *VIn) {
-
- std::vector<BasicBlock *> Work;
- SmallPtrSet<BasicBlock *, 32> Visited;
- BasicBlock *VInAncestor = DT.Info[VIn].Ancestor;
- DominatorTreeBase::InfoRec &VInVAInfo = DT.Info[VInAncestor];
-
- if (VInVAInfo.Ancestor != 0)
- Work.push_back(VIn);
-
- while (!Work.empty()) {
- BasicBlock *V = Work.back();
- DominatorTree::InfoRec &VInfo = DT.Info[V];
- BasicBlock *VAncestor = VInfo.Ancestor;
- DominatorTreeBase::InfoRec &VAInfo = DT.Info[VAncestor];
-
- // Process Ancestor first
- if (Visited.insert(VAncestor) &&
- VAInfo.Ancestor != 0) {
- Work.push_back(VAncestor);
- continue;
- }
- Work.pop_back();
-
- // Update VInfo based on Ancestor info
- if (VAInfo.Ancestor == 0)
- continue;
- BasicBlock *VAncestorLabel = VAInfo.Label;
- BasicBlock *VLabel = VInfo.Label;
- if (DT.Info[VAncestorLabel].Semi < DT.Info[VLabel].Semi)
- VInfo.Label = VAncestorLabel;
- VInfo.Ancestor = VAInfo.Ancestor;
- }
-}
-
-BasicBlock *Eval(DominatorTreeBase& DT, BasicBlock *V) {
- DominatorTreeBase::InfoRec &VInfo = DT.Info[V];
-#if !BALANCE_IDOM_TREE
- // Higher-complexity but faster implementation
- if (VInfo.Ancestor == 0)
- return V;
- Compress(DT, V);
- return VInfo.Label;
-#else
- // Lower-complexity but slower implementation
- if (VInfo.Ancestor == 0)
- return VInfo.Label;
- Compress(DT, V);
- BasicBlock *VLabel = VInfo.Label;
-
- BasicBlock *VAncestorLabel = DT.Info[VInfo.Ancestor].Label;
- if (DT.Info[VAncestorLabel].Semi >= DT.Info[VLabel].Semi)
- return VLabel;
- else
- return VAncestorLabel;
-#endif
-}
-
-void Link(DominatorTreeBase& DT, BasicBlock *V, BasicBlock *W,
- DominatorTreeBase::InfoRec &WInfo) {
-#if !BALANCE_IDOM_TREE
- // Higher-complexity but faster implementation
- WInfo.Ancestor = V;
-#else
- // Lower-complexity but slower implementation
- BasicBlock *WLabel = WInfo.Label;
- unsigned WLabelSemi = DT.Info[WLabel].Semi;
- BasicBlock *S = W;
- InfoRec *SInfo = &DT.Info[S];
-
- BasicBlock *SChild = SInfo->Child;
- InfoRec *SChildInfo = &DT.Info[SChild];
-
- while (WLabelSemi < DT.Info[SChildInfo->Label].Semi) {
- BasicBlock *SChildChild = SChildInfo->Child;
- if (SInfo->Size+DT.Info[SChildChild].Size >= 2*SChildInfo->Size) {
- SChildInfo->Ancestor = S;
- SInfo->Child = SChild = SChildChild;
- SChildInfo = &DT.Info[SChild];
- } else {
- SChildInfo->Size = SInfo->Size;
- S = SInfo->Ancestor = SChild;
- SInfo = SChildInfo;
- SChild = SChildChild;
- SChildInfo = &DT.Info[SChild];
- }
- }
-
- DominatorTreeBase::InfoRec &VInfo = DT.Info[V];
- SInfo->Label = WLabel;
-
- assert(V != W && "The optimization here will not work in this case!");
- unsigned WSize = WInfo.Size;
- unsigned VSize = (VInfo.Size += WSize);
-
- if (VSize < 2*WSize)
- std::swap(S, VInfo.Child);
-
- while (S) {
- SInfo = &DT.Info[S];
- SInfo->Ancestor = V;
- S = SInfo->Child;
- }
-#endif
-}
-
-}